## Why
V8 source and release artifacts require different ABI and C++ runtime settings. Selecting a named artifact should also select its required settings, without callers coordinating separate sandbox, pointer compression, libc++, and CPU flags.
## What changed
- Add Bazel transitions for `source`, `release`, and `sandbox_release` profiles. Source builds use the sandbox ABI and workspace runtime; release pairs use Chromium's pinned runtime with their respective ABI.
- Select the V8 CPU from the artifact target and enforce matching target platform constraints.
- Make the underlying V8 settings unavailable as CLI flags and remove redundant configuration from release tooling and workflows.
- Select Darwin/Linux prebuilts solely through `rusty_v8_from_source`, keeping source archives and bindings paired when enabled.
GitOrigin-RevId: f72fc06b6f74b79ab2ab8ca697e4f2006076a833
Sean Huang
108cf2975a